The present invention relates to a method and apparatus for splicing two pieces of drip irrigation tape together.
Drip tape, which is commonly made of polyethylene, often needs to be spliced for various reasons. First, if it is damaged after installation in the field, the damaged portion is cut out and replaced by a new length of tape which must be spliced at both ends to the cut ends of the existing tape. Second, when tape is installed along a field row, it is typically unwound from a roll of such tape. When the end of a roll is reached, the beginning of a new roll must be spliced to the end of the old roll. Finally, when drip tape is retrieved from the field for reuse at another time, it is typically spooled onto long rolls which are several thousand feet in length. Since the length of a typical field row is shorter than this, pieces must be spliced together so that the retrieved roll will be one continuous length of drip tape.
Several drip tape splicing methods are known, such as the splicing method described in U.S. Pat. No. 5,690,769 of Daigle et al. In this method, a flat insert is inserted into the end of one hose to be spliced, and the other hose end is overlapped over the first hose so that the insert also extends into the second hose end. The flat splicing insert has a bonding surface of a low melting point, bonding material, and an opposite, non-bonding surface of high melting point polyester. The overlapped hose ends are then pressed and heated between opposing heating elements, so that the hose ends fuse to each other, and to the bonding surface of the splicing insert. One problem with such flat splicing inserts is that unbonded portions may be caused to collapse into the drip tape conduit by the pressure of water flowing through the tape, potentially causing a blockage.
In U.S. Pat. No. 5,879,503 of McDunn et al, an insert of high temperature plastic is placed inside the tube ends with the tube ends adjacent one another. A bonding material is then centered over the adjacent tube ends, and heated clamp jaws are closed over the resultant assembly. This melts the bonding material to attach the tubes together, while the high temperature insert prevents the tubes from sealing together to seal the conduit closed. However, the insert remains loose in the conduit after sealing is complete, and will be pushed downstream by water forces when the tape is in use.
It is an object of the present invention to provide a new and improved drip irrigation tape splicing apparatus and method.
According to one aspect of the present invention, a method of splicing together the ends of two lengths of drip irrigation tape is provided, which comprises the steps of placing a tubular insert having an inner layer of high melting point material and an outer layer of bonding material into the end of a first length of drip irrigation tape so that a portion of the insert projects outwardly from the end of the tape, placing the end of a second length of drip irrigation tape over the projecting end of the tubular insert so that the second tape end is positioned adjacent the end of the first length of tape, and sealing both lengths of tape to the outer bonding layer of the insert.
The tubular insert may be an integral two layer insert with the layers bonded together. Alternatively, it may comprise two separately formed cylindrical insert layers, with a smaller diameter, higher melting point inner insert layer being inserted into a larger diameter, lower melting point outer insert layer, prior to insertion of the insert assembly into one of the tape ends. The separate layers may be color coded for ease of assembly, and notches may be provided for engagement when the two insert layers are in proper register.
In one embodiment of the invention, the outer layer of the tubular insert is a low melting point plastic material such as polyethylene, and each length of tape is gripped over and pressed over the insert between a pair of opposed, heated clamping jaws so that the tape is melted and fused to the outer surface of the insert. Application of pressure collapses opposing portions of the tape and enclosed insert inwards, pressing the inside of the tape against the outer bonding layer and pressing opposing portions of the inner, high melting point material against each other, so that the conduit cannot fuse closed. Alternatively, the bonding material may be an adhesive coating the outside of the tubular insert, and the two lengths of tape may be simply gripped over the insert by clamping jaws such that the adhesive bonds each length of tape to the insert. In another alternative, instead of two pairs of clamping jaws, a single heated clamping jaw is used to create a single seal at the point where the two lengths of drip tape butt up against each other, simultaneously sealing both ends to the outer layer of the insert. After creating the seals, the jaw or jaws are cooled to allow the seals to cure.
According to another aspect of the present invention, a splice apparatus for splicing the ends of two pieces of drip irrigation tape is provided, which comprises a tubular insert for insertion into the ends of the two pieces of tape with the ends placed adjacent one another over the insert, the insert having an inner cylindrical layer of high melting point material and an outer layer of bonding material, and a clamp assembly for gripping the tape pieces over the insert to bond each tape to the outer bonding layer of the insert.
In one exemplary embodiment, the outer layer is of a low melting point plastic material for forming a seal with the tape material, and the clamp assembly has opposing heated jaws for melting the outer layer of the insert and bonding the tape pieces to the insert. The clamp may comprise two spaced pairs of opposing heated jaws, one pair for gripping and sealing a first piece of drip tape over the insert adjacent the end of the drip tape, and the other pair for gripping and sealing the second piece of drip tape over the insert adjacent the end of the second piece, forming two spaced circumferential seals.
In this method and apparatus, since the insert is tubular and has a high temperature melting point inner layer, the conduit cannot be blocked by the insert. The tape ends will be sealed to the outer layer of the insert, while the inner layer of high melting point material will remain unmelted and will not fuse to itself. Additionally, because the drip tape pieces are sealed to the insert and not to each other, the method is less dependent on the properties of the drip tape being sealed, so that it can be more universally applied. The low melting point outer layer of the insert can be selected to be made of a material which melts easily and forms a good seal with most drip tapes. The lower melting point material results in less energy required to form the seal.
The tubular insert can be made rigid enough that it is not caused to collapse into the drip tape conduit by water flowing through the tape. This is not the case with flat inserts employed in prior art methods. Since the insert positively adheres to the drip tape it is sealed to, it cannot be pushed downstream by water forces within the tape, as with some prior art flat inserts.